Cartilage Innate Immunity in Osteoarthritis

摘要 项目摘要： 原始Toll样受体（TLR）介导的先天性免疫应答触发并形成许多炎性和非炎性免疫应答。 免疫系统紊乱IL-1诱导软骨细胞中的TLR 2和TLR 4，并且这两种TLRs在OA软骨中均增加 在原地。此外，微生物TLR 2和TLR 4配体刺激软骨细胞中的分解代谢反应。我们 初步数据显示，共有的TLR和IL-1受体衔接蛋白MyD 88（而不是可溶性IL-1）， 受体拮抗剂）减弱所有在软骨中测试的炎症诱导的分解代谢和分化反应 外植体和培养的软骨细胞。我们进一步观察到TLR 2、TLR 4双敲除（TLR 2/4 dKO） 小鼠软骨外植体和软骨细胞保持IL-1反应性，但对低浓度IL-1失去反应性。 分子量透明质酸低聚糖（LMW-HA）和HMGB 1，两种内源性TLR 2和TLR 4 存在于OA关节中的配体。此外，TLR 2/4 dKO小鼠软骨细胞失去了在软骨细胞中安装一个细胞因子的能力。 软骨细胞中的分解代谢反应，不仅透明质酸酶-2的表达增加， LMW-HA形成，但也有HMGB 1。这一提议的核心假设是， TLR 2和TLR 4信号传导的结合在体外和体内都具有软骨保护作用，并提供了新的手段， 开发改善疾病的OA疗法。我们将在体外研究软骨外植体的反应， 软骨细胞与LMW-HA和HMGB 1的结合，以确定TLR 2和TLR 4信号传导如何促进软骨细胞 不仅使用MyD 88，而且使用选择性需要的TIRAP/Mal， 用于TLR 2和TLR 4信号传导。我们还将使用手术不稳定诱导的膝关节OA进行体内研究 模型，以评估OA进展是否被TLR 2和TLR 4的双重敲除抑制，或者被TLR 2和TLR 4的双重敲除抑制。 TIRAP/Mal的单敲除，并且如果MyD 88的敲除具有比IL-1的敲除更好的上级保护作用 抑制OA的受体。这些研究的完成将提供新的见解，以了解先天免疫如何 软骨中炎性反应促进OA进展并提供至少一种潜在的药物治疗 以有效改善OA疾病为目标。 相关性： 骨关节炎（OA）是最常见的与衰老有关的关节疾病。OA的进展是由低- 软骨分级炎症。白细胞介素-1（IL-1）是一种炎症介质，可促进OA的进展， 但是通过IL-1抑制抑制OA的结果还不完全。迫切需要确定 IL-1以外的介质驱动OA进展，以开发真正有效的疾病调节 治疗这种疾病。

Abstract Project Summary: Primitive Toll-like receptor (TLR)-mediated innate immune responses trigger and shape many inflammatory and immune disorders. IL-1 induces TLR2 and TLR4 in chondrocytes and both TLRs are increased in OA cartilage in situ. Moreover, microbial TLR2 and TLR4 ligands stimulate catabolic responses in chondrocytes. Our preliminary data reveal that the shared TLR and IL-1 receptor adaptor protein MyD88 (but not soluble IL-1 receptor antagonist) blunts all inflammation-induced catabolic and differentiation responses tested in cartilage explants and cultured chondrocytes. We further observe that TLR2, TLR4 double knockout (TLR2/4 dKO) mouse cartilage explants and chondrocytes retain IL-1 responsiveness, but lose responsiveness to low molecular weight hyaluronan oligosaccharides (LMW-HA) and HMGB1, two endogenous TLR2 and TLR4 ligands present in OA joints. In addition, TLR2/4 dKO mouse chondrocytes lose the capacity to mount a catabolic response in chondrocytes with increased expression of not only hyaluronidase-2 which catalyzes LMW-HA formation but also HMGB1. The central and translational hypothesis of this proposal is that inhibition of both TLR2 and TLR4 signaling is chondroprotective both in vitro and in vivo and offers novel means to develop disease-modifying OA therapy. We will perform in vitro studies on responses of cartilage explants and chondrocytes to LMW-HA and HMGB1 to determine how TLR2 and TLR4 signaling promotes chondrocyte hypertrophy and cartilage catabolism using not only MyD88, but also TIRAP/Mal which is selectively required for TLR2 and TLR4 signaling. We will also perform in vivo studies using a surgical instability-induced knee OA model to assess if OA progression is suppressed by dual knockout of TLR2 and TLR4, and alternatively by single knockout of TIRAP/Mal, and if knockout of MyD88 has superior protective effects than knockout of IL-1 receptor for OA suppression. Completion of these studies will provide new insights into how innate immune inflammatory responses in cartilage promote OA progression and provide at least one potentially druggable target for effective OA disease modification. Relevance: Osteoarthritis (OA) is the most common joint disease related to aging. Progression of OA is promoted by low- grade inflammation in cartilage. Interleukin-1 (IL-1), an inflammatory mediator, promotes the progression of OA, but results have been incomplete for suppression of OA via IL-1 inhibition. There is a pressing need to identify mediators beyond IL-1 that drive OA progression, in order to develop true and effective disease modifying treatment of this disease.